Antibacterial properties of composite resins incorporating silver and zinc oxide nanoparticles on Streptococcus mutans and Lactobacillus

OBJECTIVES: Recurrent caries was partly ascribed to lack of antibacterial properties in composite resin. Silver and zinc nanoparticles are considered to be broad-spectrum antibacterial agents. The aim of the present study was to evaluate the antibacterial properties of composite resins containing 1% silver and zinc-oxide nanoparticles on Streptococcus mutans and Lactobacillus. MATERIALS AND METHODS: Ninety discoid tablets containing 0%, 1% nano-silver and 1% nano zinc-oxide particles were prepared from flowable composite resin (n = 30). The antibacterial properties of composite resin discs were evaluated by direct contact test. Diluted solutions of Streptococcus mutans (PTCC 1683) and Lactobacillus (PTCC 1643) were prepared. 0.01 mL of each bacterial species was separately placed on the discs. The discs were transferred to liquid culture media and were incubated at 37degrees C for 8 hr. 0.01 mL of each solution was cultured on blood agar and the colonies were counted. Data was analyzed with Kruskall-Wallis and Mann-Whitney U tests. RESULTS: Composites containing nano zinc-oxide particles or silver nanoparticles exhibited higher antibacterial activity against Streptococcus mutans and Lactobacillus compared to the control group (p < 0.05). The effect of zinc-oxide on Streptococcus mutans was significantly higher than that of silver (p < 0.05). There were no significant differences in the antibacterial activity against Lactobacillus between composites containing silver nanoparticles and those containing zinc-oxide nanoparticles. CONCLUSIONS: Composite resins containing silver or zinc-oxide nanoparticles exhibited antibacterial activity against Streptococcus mutans and Lactobacillus.

Effect of Epigallocatechin Gallate on shear bond strength of composite resin to bleached enamel: an in vitro study

OBJECTIVES: The aim of this study was to determine the effect of epigallocatechin gallate (EGCG) on the shear bond strength of composite resin to bleached enamel. MATERIALS AND METHODS: Ninety enamel surfaces of maxillary incisors were randomly divided into 9 groups as follows: G1: control (no bleaching); G2: bleaching; G3: bleaching and storage for seven days; G4 - 6: bleaching and application of 600, 800 and 1,000 micromol of EGCG-containing solution for 10 minutes, respectively; G7 - 9: bleaching and application of 600, 800 and 1,000 micromol of EGCG-containing solution for 20 minutes, respectively. The specimens were bleached with 30% hydrogen peroxide gel and a composite resin cylinder was bonded on each specimen using a bonding agent. Shear bond strength of the samples were measured in MPa. Data was analyzed using the two-way ANOVA and Tukey HSD tests (alpha = 0.05). RESULTS: The maximum and minimum mean shear bond strength values were observed in G1 and G2, respectively. Time and concentration of EGCG showed no significant effects on bond strength of the groups (p > 0.05). Multiple comparison of groups did not reveal any significant differences between the groups except for G2 and all the other groups (p < 0.05). CONCLUSIONS: There is a significant decrease in bond strength of composite resin to enamel immediately after bleaching. A delay of one week before bonding and the use of EGCG increased bond strength of composite resin to bleached enamel.

Erratum - Effect of ascorbic acid, ethanol and acetone on adhesion between the treated fiber posts and composite resin cores

The author names were mistakenly given as Khamverdi Zahra and Talebian Reza. It should be corrected as Zahra Khamverdi and Reza Talebian.

Effect of ascorbic acid, ethanol and acetone on adhesion between the treated fiber posts and composite resin cores.

PURPOSE: The aim of the present study was to assess the effect of ascorbic acid, ethanol and acetone on microtensile bond strength between fiber posts pre-treated with hydrogen peroxide and composite resin cores. MATERIALS AND METHODS: Twenty four fiber posts were pre-treated with 24% hydrogen peroxide and divided into 4 groups as follows: G1: no treatment, as control group; G2: treatment with 10% ascorbic acid solution for 5 minutes; G3: treatment with 70% ethanol solution for 5 minutes; and G4: treatment with 70% acetone solution for 5 minutes. Each fiber post was surrounded by a cylinder-shaped polyglass matrix which was subsequently filled with composite resin. Two sections from each sample were selected for microtensile test at a crosshead with speed of 0.5 mm/min. Statistical analyses were performed using one-way ANOVA and a post hoc Tukey HSD test. Fractured surfaces were observed under a stereomicroscope at ×20 magnification. The fractured surfaces of the specimens were observed and evaluated under a SEM. RESULTS: MEANS OF MICROTENSILE BOND STRENGTH VALUES (MPA) AND STANDARD DEVIATIONS IN THE GROUPS WERE AS FOLLOWS: G1: 9.70±0.81; G2: 12.62±1.80; G3: 16.60±1.93; and G4: 21.24±1.95. G4 and G1 had the highest and the lowest bond strength values, respectively. A greater bond strength value was seen in G3 compared to G2. There were significant differences between all the groups (P<.001). All the failures were of the adhesive mode. CONCLUSION: Application of antioxidant agents may increase microtensile bond strength between fiber posts treated with hydrogen peroxide and composite cores. Acetone increased bond strength more than ascorbic acid and ethanol.